I took a cab from Bedford station to Yarl’s Wood last Sunday. Britain’s biggest immigration detention centre for women is on the edge of a business park in the middle of the countryside. The guard at the gate said there were ‘people around the premises’ when I asked him about the protest I’d come to join, but he wouldn’t tell me where they were. ‘I’m going to have to ask you to leave,’ he said. I walked away through the business park, past a giant warehouse that looked like an empty distribution centre, past the Red Bull Racing wind tunnel, until at last I saw a group of people protesting by a gate. But I was inside the business park and they were on the other side of the fence.

I got a lift from a couple who’d got lost on the way from London for a meeting with a relative inside Yarl’s Wood. Because they were late they were only allowed to see her for half an hour. They dropped me off and I walked for a while before getting another lift from a man who was looking for his dog.

By the time I joined the protest, there were 40 to 50 people standing by the closed gate. Most of them were women, along with a few men and two children. The business park is on private land. This was the closest the protesters could get to the building. Cristal Amiss from Black Women’s Rape Action Project, who had called for the protest, was speaking on the phone to women detained inside. The phone was plugged into a loud speaker so that everybody could hear.

The previous weekend there had been a small demonstration outside Harmondsworth detention centre, near Heathrow, following a mass hungerstrike of detainees in protest against the fast-track removal procedure. There, too, people inside took part in the demo, through the phone. At Yarl’s Wood we could see in some of the windows, behind the wall and the double barbed-wire fence, people waving at us and holding signs. Both detention centres are privately run: Harmondsworth by the GEO Group, Yarl’s Wood by Serco.

‘People are being treated like animals,’ a woman said on the phone. Detainees have denounced poor access to healthcare, abusive guards and a dysfunctional system. At the heart of it all, there is a culture of disbelief, according to Debra from SOAS Detainee Support. ‘People will tell the truth, what their perception of the truth is, and won’t be believed, even if they’re saying the same thing over and over again,’ she said. ‘They will say they are in pain and be told: Here is some Paracetamol.’ SDS have been visiting people in detention centres, offering support by phone and helping them to find lawyers.

Some of the protesters were women who had been detained in Yarl’s Wood. They recognised the current detainees’ concerns, even the names of abusive nurses or guards. For them, little seems to have changed.

‘The sexual abuse is not a new question,’ according to Antonia Bright from Movement for Justice, who organised the Harmondsworth protest. ‘What is new is the number of people speaking about it.’

In April, Rashida Manjoo, the UN special rapporteur on violence against women, who had received reports of violations in Yarl’s Wood, said she was barred at the gates on instructions ‘from the highest level of the Home Office’. In her preliminary report, she wrote:

A large number of women in detention have a history of being subjected to violence prior to being imprisoned… the strong link between violence against women and women’s incarceration, whether prior to, during or after incarceration, needs to be fully acknowledged.

In May, Serco was forced to disclose an internal report revealing it had failed to investigate properly a claim of repeated sexual assault by one of its staff against a female detainee at the centre. According to the report, a Serco guard who believed the alleged victim’s claims was to be given ‘guidance’; the alleged victim was thought to lack credibility because her allegations were too consistent and too detailed.

On Sunday, one woman was holding a sign that showed Angelina Jolie and William Hague (who had co-chaired the Global Summit to End Sexual Violence in Conflict the week before in London). On the banner, Jolie was thinking: ‘Does he know about sexual assaults in Yarl’s Wood?’ Hague’s response: ‘Yeah, but am I bovvered?’

Meanwhile, a young woman on the phone was explaining that she would be removed soon, to a country she doesn’t know, and accusing Serco of ignoring the serious health concerns of one of her relatives. Her voice was breaking. She said that people who didn’t speak English were treated worse.

‘Women in Yarl’s Wood have faced every form of violence and deprivation, every possible form of sexism,’ Bright told me. ‘This place is a battleground in the struggle for women’s rights. It needs to shut down. There is no way to make it nicer.’

‘Women of Yarl’s Wood, we are with you!’ the crowd chanted. ‘Teenagers in Yarl’s Wood, we are with you! Mothers in Yarl’s Wood, we are with you! Raped women in Yarl’s Wood, we are with you! Pregnant women in Yarl’s Wood, we are with you!’

They walked to the gate and shook it for a long time, really noisily. A man put Gloria Gaynor’s ‘I Will Survive’ on to play over the PA system, mixing the disco anthem with the loud banging of the gate.